The Manyara monkey (Cercopithecus mitis manyaraensis) has a geographic range extending between 1,500 and 5,900 square kilometers (580 to 2,200 square miles) around Lake Manyara, a stretch of waterland covering patches of Manyara region upper part and Arusha region lower part.
The ecosystems here, including groundwater, mid-altitude and montane forests at elevations of 960 to 2,550 meters (3,150 to 8,370 feet), are relatively understudied. But based on other studies of Cercopithecus, the genus also known as gentle monkeys, it is likely that the Manyara monkey is an important disperser of forest tree seeds and an important consumer of invertebrates.
Yvonne de Jong and Tom Butynski, who identified the subspecies, said they had already assessed it as endangered in the red list issued by the International Union for the Conservation of Nature (IUCN).
“All of the documented current threats to the long-term survival of Tanzania’s primates are directly or indirectly related to human activities — degradation, loss, and fragmentation of forest, poaching, loss of wildlife corridors, setting of fire, and invasion of exotic plants, to name a few,” de Jong told Mongabay. “Even the threat of climate change appears to have humans as the root-cause.”
Primatologists consider Tanzania one of the most important countries in the world for primate conservation, given its large number of non-human primates. It is home to 14 genera, 28 species and 44 species and subspecies, of which no fewer than 13 taxonomic varieties are found nowhere else.
Eleven of Tanzania’s primate species and eight of its subspecies are classified as threatened on the IUCN Red List.
Forest-dependent species varieties such as gentle monkeys are at particular risk. Gentle monkeys, sometimes also called greater periphery monkeys, are large, long-tailed, tree-dwelling monkeys found across Southern and East Africa. Their habitat is evergreen forest at various altitudes, and they are known to have highly developed arboreal skills compared to some other types of monkey.
De Jong and Butynski, who assessed the Manyara monkey for the IUCN Red List of Threatened Species 2020, concluded that this subspecies is endangered despite the fact that about 60% (around 3,500 km² or 1,350 mi2) of its probable geographic distribution lies within six protected areas.
Writing about their 15-year study and identification of the subspecies in the journal Primate Conservation at the end of the April, the pair called for improved management of the protected areas in which the Manyara monkey occurs as well as the restoration and protection of the wildlife corridors of the Lake Manyara-Ngorongoro region.
“The threats to the Manyara monkey are particularly serious in non-protected areas,” Butynski told Mongabay. “Connectivity among the six protected areas in which the Manyara monkey is known to occur is threatened, and this connectivity is essential for maintaining healthy populations. Fragmentation of wild populations creates many expensive and complicated conservation and management problems.”
He attributed the loss of connectivity largely to agricultural expansion, as well as new settlements, roads and other infrastructure driven by a rapidly growing population; Tanzania’s population is expected to more than double by 2050.
“Effective management of the six protected areas in which the Manyara monkey occurs, and the restoration and protection of the wildlife corridors of the Lake Manyara-Ngorongoro region, are essential to the conservation of this new subspecies and other wildlife in the region,” Butynski said.
Other experts say the identification of the subspecies, and its recognition as being endangered, could provide it with some protection.
“Having a species classed as endangered can actually do some good as it brings attention to it — it gains national and international attention, authorities pay attention to it, researchers start studies, which can add to its overall protection while other measures are considered,” Gráinne McCabe, head of conservation science at the Bristol Zoological Society in the U.K., told Mongabay.
Butynski agreed that identifying the subspecies could help in its future protection. “Simply said, you need to know what taxa are where, and their conservation status, to be able to effectively protect them,” he said. But he added it also had a deeper significance as primates come under increasing threat.
De Jong and Butynski note that Tanzania is losing about 200 km2 (77 mi2) of forest each year (at 1.1%, it’s the second-highest annual rate of forest loss in sub-Saharan Africa) and has a 3% human population “rate of natural increase” (compared to 1% worldwide). They say it is therefore inevitable that Tanzania will continue to lose large areas of forest and large numbers of forest-dependent primates.
“Tanzania’s human population, now about 60 million people, is projected to increase to more than 90 million by 2036, and to more than 129 million by 2050. Where will Tanzania get twice as much food, clean water, energy, and other resources to provide to twice as many people in 30 years?” Butynski said.
This makes classifying species and subspecies, including the new Manyara monkey, even more important.
“We are obliged to find out what plants and animals are out there, and to ensure that they are formally recognized so that they have a voice as concerns their long-term viability and place in natural ecosystems,” de Jong said. “Many taxonomic varieties have been driven to extinction over the past century and these will, no doubt, be joined by many others during the 21st century.
“Their loss will have simplified ecosystems forever — and made those who depend on these ecosystems more vulnerable to the same fate, including humankind.”